US2473518A - Pressure breathing mask for aviation - Google Patents

Description

June 21, 1949.

H. F. GAR RARD EIAL PRESSURE BREATHING MASK FOR AVIATION Filed Dec. 16, 1946 IN VEN TORJ. HOW/4E5 Ff 6458460 BY WK-FL K 50F Patented June 21, 1949 ll STATES PATENT ()FFICE PRESSURE BREATHING MASK FOR AVIATION Howard F. Garrard, Osborn, and Earl V. Rupp, Dayton, Ohio amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to us of any royalty thereon.

This invention relates to a pressure-breathing mask especially intended for aviation, although p ssu e-b at ng mask that may be used at exit may be used for other purposes. tremely low temperatures for periods of four hours At altitudes in excess of 35,000 feet, it is necesor more. sary to supply oxygen pressure above the am- Another object is to provide such a mask in bient pressure. Such oxygen pressure must inwhich electrical heating s un c y. crease as the altitude increases up to about 50,000 Another object is to provide a mask having feet, where it is necessary to apply some form of the inhalation and exhalation valves outside the counter pressure to the body to counteract the ce cav ty of e a a d a d to unct on h pressures necessary for inhalation. This ooperatively. invention is concerned with the structure of oxy- In the drawing, I0 is a mask body or facepiece gen masks suitable for pressure breathing. Prewhich may be of the U. S. Army Air Forces Type viously the mask that has been used by the Army A 3 mask. Such a mask is used for the inhala- Air Forces is designated Type A-l3. It generally tion of oxygen under pressure at high altitudes. comprises a facepiece, two inhalation ports, each The body l0 contains an exhalation valve body controlled by inhalation valves mounted in the II and an inhalation valve body l2. There is an iacepiece at the ports, and a, pneumatically balinhalation port l3 in the body l0 and an outanced or compensating type of exhalation .valve. side passage [4 (shown in dashed lines) connect-j This valve operates by being responsive to the ining the port l3 with a rubber inlet tube i5 in crease in pressure produced by exhalation, the which the inhalation valve body I2 is held. A higher inhalation pressures being balanced by the cavity H5 in the mask o y "I s nt ded fo application of inhalation pressure to the under a microphone and has no bearing on the present side of a diaphragm as well as on the opposite invention. H is an exit port for exhaled air. or facepiece side. The diaphragm is a part of Black arrows indicate the direction taken by exthe exhalation valve. The exhalation valve opens haled gas s; white arrows the path of the o y en by the increase in pressure produced by exhalato be inhaled. tion and confined within the mask by the inhala- Within the inhalation valve body l2, there is tion valve. a valve seat l8 which may be an integral part One of the principal difficulties in connection of the body l2. The valve seat I 8 is provided with the operation of the Type A-13 mask is that with a sharp upwardly projecting flange or seat the inhalation valves have been afiected consid- I9 and a central boss 20 which holds a soft ruberably by condensation of moisture, which freezes and interferes with the seating of the valve. Many devices have been provided, which have assisted to some extent, in continuing the proper functioning of the mask. In the prior art, such devices have been deflectors over the valves and heating pads placed at points where freezing usually occurs. The time through Which a mask could. be used at extremely low temperatures has not, until the present invention, exceeded more than one hour. Upon freezing, the valves tend to leak and allow the exhalation pressure to be dissipated through the valve and into the inhalation port, thereby preventing the exhalation valve from opening.

Another expedient has been the provision of heating coils about the base on which the valve operates, but all these methods of protection or heat application are distinctly disadvantageous in view of the fact that heating coils may become inoperative. Heating also places an additional load on the electrical system of the aircraft and is a further accessory that requires attention on the part of the wearer.

One object of the invention is to provide a ber flap or check-valve 2| so that the latter may seat upon or lift from the flange l9.

Extending through the boss 22, there is a tube 22 which connects the source of oxygen under pressure through a regulator (not shown) below the inhalation valve with a space 23 exposed to the atmosphere. The purpose of the tube is to apply inlet pressure to the underside of the diaphragm 26.

The exhalation valve body II is provided with a central sharp-edged, downwardly projecting flange or seat 24 and an outer flange 25 concentric with flange 24. Attached to the flange 25 is a compound or double soft rubber diaphragm 26 separated by a weak spring 35. The top member 25a of valve 26 normally is in contact with the sharp edges of flange 24 except when the wearer of the mask is exhaling. Then it is forced downward by exhalation pressure, thus opening the valve to atmosphere through openings .33 and N in the body H. The center portion of valve seat 26a is stifiened between metallic plates, the top one of which is 2'! and the bottom one 210.. Plate 21 is of smaller diameter than plate 21a. The latter is large enough so that it will extend slightly beyond the sharp edges, thus providing a tight seal of small contact area.

26b is the bottom portion of valve 26. It is fastened to the top portion 26a at the edges. A corrugation 28 defines a circle in the lower portion of valve 2%. The corrugation 28 rests on a removable mushroom-shaped member 29 to the lower part of which the tube 22 is attached. A channel 30 extends upwardly through member 29 and continues the bore of tube .22. Channel 30 terminates in a flat space 31 under a small plate 32 which prevents valve 26b from closing off communication of the space 23 with the interior of valve body It.

In operation, the inlet pressure to the mask is applied to the underside of the exhalation valve through the tube 22. Application of inlet or inhalation pressure to the underside of the valve causes the exhalation valve to close the outlet by the application of the added pressure produced by exhalation. Inlet pressure is applied to the top or mask side of the exhalation valve diaphragm 23 through the inlet port l3. Upon exhalation the increase in pressure in the mask over inlet pressures is sufficient to open the exhalation valve to allow the exhaled air to be discharged to the atmosphere. Such action of the valve causes a compression of the spring 35 joining the two diaphragms 26a and 26b. The spring 35;is so weak that the pressure of exhalation .can flatten it.

.A breathing cycle produces the following action: During inhalation oxygen passes up through the tube ,22 from a hose joined to an oxygen pressure regulator (not shown). This inlet pressure is applied to the exhalation valve. Pressures are established in the mask depending on the operation of the regulator which may range from .1 to .20 of water in the mask, this depending on the altitude and pressure required. Upon completion of inhalation and the start .of exhalation, the increase in pressure is suflicient to open the exhalation valve diaphragm 26 and the check valve 2| operates to establish the .exhalation pressure in the mask since it is disposed adjacent the mask and the total volume of the inlet tube from the check valve to the mask and the inner .mask volume involved are not great enough to cause dissipation of pressure to prevent opening of the valve. Consequently, the slight increase in pressure causes the exhalation valve to open to the atmosphere and to vent the exhaled gases from the mask.

A mask of the foregoing description has been used at a temperature of 55 F. for a period of more than four hours without any accumulation of moisture about the valves and during this time the mask functioned satisfactorily. A small accumulation of snow occurred in the exhalation ports, but this was not of suificient consequence to interfere with the operation of the mask.

The mask herein described has other advantages than freedom from freezing, but :its coldproof characteristics are due primarily to the arrangement and location of the valves, includingtheir sharp seating edges.

passage from the mask and can be opened only The invention claimed is:

In combination in an oxygen pressure mask, a mask body including a downwardly extending tube of substantial bore size, an inlet tube extending up one side of the mask body and connecting the upper part of said downwardly extending tube with an opening in the side of the mask body, an exhalation vent between the upper part of said tube and said mask body, said exhalation vent being out of communication with said tube, an inhalation valve connected to the lower part of said tube, an exhalation valve in the lower part of said mask body over said tube and in communication with said exhalation vent and a tube extending through said inhalation valve and to the lower interior of said exhalation valve whereby to equalize the oxygen pressures existing in the mask body and the lower interior of said exhalation valve.

2. A mask according to claim 1 in which the inhalation and exhalation valves are of the diapbragm type and each have at least ,one sharp edged sea 3. 'In an oxygen pressure mask having a mask body, an exhalation valve communicating with the atmosphere and pressure responsive expansible chamber means for loading said exhalation valve during an inhalation period, the improvement which comprises an inlet conduit at the lower portion of said mask body, inlet passage means connected to said conduit and terminating in a port communicating with the interior of the mask, an inlet valve means positioned within the inlet conduit below the connection of the inlet passage means therewith for operation in a region removed from exhaled air containing moisture, and a conduit connected to said inlet conduit on the supply side of said inlet valve and communicating with said expansible chamber means to provide loading pressure to said exhalation valve.

4. In an oxygen pressure mask having a mask body which contains a difierential pressure responsive exhalation valve communicating with the atmosphere positioned to be subjected to mask pressure and inlet pressure simultaneously, the improvement which comprises an inlet conduit at the lower portion of said mask body, inlet passage means connected to said conduit and terminating in a port communicating with the interior of the mask body, an inlet check valve positioned within the inlet conduit below the connection of the inlet passage therewith, and a conduit connected .to said inlet conduit on the supply side of said inlet check valve and communicating withsaid difierentialpressure responsive exhalation valve to provide loading pressure to said exhalation valve whereby condensation moisture of the exhaled air does not aiiect the inlet check valve. I

HOWARD F. GARRARD. EARL V. RUPP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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